Self-regulating dynamo



(No Model.)

I. N. LEWIS. SELF REGULATING DYNAMO.

No. 516,497. Patented Mar. 13, 1894.

Wm 11111 c.

Uwrrnn STATES PATENT OFFICE.

ISAAC N. LEIVIS, OF FORT W'ADSWORTH, NEYV YORK, ASSIGNOR TO THE LEIVISELECTRIC COMPANY, OF NEW JERSEY.

SELF-REGULATlNG DYNAMO.

SPECIFICATION forming part of Letters Patent No. 516,497, dated March13, 1894.

Application filed September 6, 1893. Serial No. 484.898. (No model.)

T0 whom it may concern:

Be it known that I, ISAAC N. LEWIS, a citizen of the United States, anda resident of Fort Wadsworth, in the county of Richmond and State of NewYork, have invented a certain new and useful Self-Regulating Dynamo, ofwhich the following is a specification.

My invention relates more particularly to dynamo electric machinesoperated by apower which drives the machine at a varying or fluctuatingspeed.

As is well known the voltage or output of a dynamo of ordinaryconstruction will, other things being equal, rise with the speed ofrotation of its armature.

The principal aim of my invention is to secure a practically constantvoltage or output lrrespective of the speed.

As will be apparent the invention applies especially to cases where thecurrent demanded of the machine for operating the translating device ordevices, is practically constant in amount.

My invention consists in a method of automatically regulating a dynamomachine to deliver a substantially constant potential irrespective ofthe speed by increasing the strength of a current which cuts down thefield magnetism with an increase of speed and vice versa, therebyautomatically regulating the voltage so that any tendency to increasethereof with increase of speed will be practically compensated for bythe decrease of the magnetic field.

In carrying out my invention the opposing or neutralizing current whichresponds to or varies automatically with the speed may be obtained andapplied inany way, the only essential being that it shall rise with therise of speed in sufficient amount or in such ratio to the mainmagnetizing power that the strength of the field magnetism shalldecrease and thereby keep down the voltage. The most obvious and simplemanner of obtaining and applying such current is to include an opposingor demagnetizing coil in a circuit with the armature of the machine, theeffect being that the higher the speed of the armature and the higherthe voltage thereof the greater the current which will flow in saidcoil. 1 do not limit myself, however, to using the armature current ofthe machine itselfor to varying the opposing currentby variations in thevoltage of the armature itself, since, as will be obvious, the increaseof current might be brought about in other ways where the speed rises.

As will be obvious a dynamo having its voltage governed in accordancewith my invention in its simplest form may be said to be a compoundwound dynamo having its series coil reversed or so proportioned in itseffect to another source of field magnetism that the increased currentpassing through the series coil upon an increase of speed weakens themagnetic field and thereby keeps the voltage down at the increasedspeed. The field magnetism may be obtained either in shunt from thearmature of the machine or from any other independent source, but Iprefer to use an independent or separate source of excitation whichdetermines the polarityof the machine and is practically constant orvaries only in such degree as not to prevent the increased current inthe main from cutting down the field strength at the increased speed.The shunt coil may, as well understood in the art, be a shunt across thebrushes of the armature direct or may be a shunt across the wholeexternal circuit and as will be presently explained in connection withthe drawings: wherein Figure 1, is a diagram illustrating a machineadapted for carrying out my invention; and Fig. 2,a diagram ofanotherarrangement of circuits.

In the drawings A, typifies the armature and B, the field magnet.

0, indicates the translating device or devices which are operated bycurrent taken from the armature and delivered thereto over the wires orconnections a, b.

D, in Fig. 1, is a field magnet coil which forms the principal fieldenergizing coil of the machine and is supplied with current from anydesired source. In Fig. 1, I have shown it as connected at the pointsat, y, to the circuit a, Z), so as to be fed in shunt to the wholeexternal circuit. lVhen so fed as a shunt it is preferably made of finewire as well understood in the art. The said principal coil might,however, be fed from an independent source typified at E, as a storagebattery or other generator of electricity. E, is the regulating coilwhich in Fig. l, is illustrated as a main circuit coil so that itscurrent will vary directly with any variation of voltage of the armatureitself. The coil E, as shown, is wound reversely to the coil B, so as toact as a demagnetizing or opposing coil tending to cut down the fieldmagnetism and, therefore, to reduce the voltage of the armature. Theproportioning of the effects of the two coils by the number of turns andtheir resistance is made such that when the voltage of the armaturerises from increase of speed the opposing cifects of the main circuitcoil shall rise in proper ratio with respect to any increase of currentin the other coil, to result in the production of a field which isweaker with the increase of speed. As will be seen any tendency toincrease of voltage of the armature due to increase of speed will bethereby automatically com pensated for as the increased current therebyflowing in coil E, will cut down the field magnetism and bring thevoltage or electro-motive force of the armature back to normal.

It will be understood by electricians that the proportions of thevarious coils are to be determined by the particular circumstances ofeach case. I have shown the regulating coil E, as wound directly uponthe field mag- V netitself but, as well understood by electricians itmight be applied in other ways or in other positions so as to have theefiect, when the increased current flows through it, of cutting down theelectro-motive force in the armature coils. that the use of the coil inthe manner shown directly upon the field magnet is simply typi-' cal ofany coil that operates in a similar mannor to control the voltage orelectro-motive force of the armature when the speed increases.

In the diagram Fig. 2, I illustrate that modification of my inventionbefore referred to which involves the use of a principal energizing coilD, supplied in a shunt directly across the terminals of the armature.

In all cases there is of course a critical speed determined by theWinding up to which the voltage when the machine starts into operationwill increase but beyond which any further increase of speed will beaccompanied by the compensating or regulating action above described,resulting in a practical constancy of voltage although the speed mayfluctuate within any limits above such critical speed.

My invention is particularly applicable to cases where the externalresistance is low and the resistance of the armature itself is low sinceunder these conditions a small increase Hence, it is to be understood inthe voltage will produce a large increase In the amount of currentflowlng 1n the main circuit coil and when the machlue 1s shunt Woundwill produce a comparatively small increase in the derived circuit coil.

WVhat I claim as my invention is 1. The herein described method ofautomatically regulating a dynamo machine to deliver a substantiallyconstant potential when driven at variable speed, consisting inincreasing the strength of an electric current with an increase of speedand by such increased current cutting down the increment ofelectro-motive force or-voltage which would arise from the increasedspeed of rotation of the armature.

2. The herein described method of regulating the voltage or potential ofa dynamo for changes of speed in its driving power, consisting incutting down the strength of the field in which the armature rotates byincreased current from the armature of said dynamo upon an increase ofspeed.

3. The combination with a dynamo machine driven by a variable speed, ofa magnet coil in the circuit of the armature Wound or applied in themanner described to tend to cut down the voltage or electro-motive forceof the armature when the current in said coil due to increase of speedrises.

4. The combination ina dynamo electric machine delivering constantpotential irrespective of speed driving, of two field coils one of whichis the principal field energizing coil and determines the polarity ofthe machine while the other opposes the action of the first in variableamount to vary the field magnetism inversely as the speed of thearmature, as and for the purpose described.

5. The combination in a dynamo electric machine for delivering constantpotential with variable speed of driving, of two field magnet coils oneof which is the principal energizing field coil while the other iswoundto oppose the effect of the first and isconnected into the maincircuit of the armature so as to cut down the field magnetism when thespeed of the armature rises.

6. The combination, substantially as described, with a dynamo having aseparate and approximately constant excitation from any source, of anopposing main circuit field coil in the direct circuit between thearmature and the work, substantially as and for the purpose described.

Signed at New York, in the county of New York and State of New York,this 5th day of September, A. D. 1893.

' ISAAC N. LEWIS.

Witnesses:

WM. H. CAPEL, THOS. F. CONREY.

